Reland: Refactor code that defers extension background page loading

src/extensions depends on chrome::NOTIFICATION_PROFILE_CREATED to support
deferred loading of extension background pages when the profile isn't ready
yet. This is a layering violation.

* Remove Chrome concepts like "browser window ready" and "profile created"
from ProcessManager. Introduce ProcessManagerDelegate with a general concept
of deferring background page loading.
* Consolidate all the tricky Chrome-specific background page loading rules into
ChromeProcessManagerDelegate. This keeps all the rules in one place. Annotate
each block of special case code with the bug that inspired it.
* Extend unit test coverage for ProcessManager.

This will make it easier to eliminate chrome::NOTIFICATION_PROFILE_DESTROYED
in ProcessManager in a later CL.

(Original CL https://codereview.chromium.org/381283002 broke valgrind bots
because it was initializing left-over BrowserContextKeyedServices from tests
running earlier in the same process.)

BUG=392658
TEST=unit_tests ProcessManagerTest, browser_tests ProcessManagerBrowserTest, manual

Review URL: https://codereview.chromium.org/408523005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@284593 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 2 insertions, 0 deletions

diff --git a/extensions/browser/extension_registry.h b/extensions/browser/extension_registry.h
index 75724cd..d11111c 100644
--- a/extensions/browser/extension_registry.h
+++ b/extensions/browser/extension_registry.h
@@ -43,6 +43,8 @@ class ExtensionRegistry : public KeyedService {
   // Returns the instance for the given |browser_context|.
   static ExtensionRegistry* Get(content::BrowserContext* browser_context);
 
+  content::BrowserContext* browser_context() const { return browser_context_; }
+
   // NOTE: These sets are *eventually* mututally exclusive, but an extension can
   // appear in two sets for short periods of time.
   const ExtensionSet& enabled_extensions() const {